JP2011094111A - Aromatic polysulfone resin and membrane thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aromatic polysulfone resin excellent in toughness and suitable as a raw material of membranes including a porous membrane. <P>SOLUTION: The aromatic polysulfone resin has reduced viscosity of 0.55-0.65 dL/g, preferably 0.58-0.62 dL/g, a number-average molecular weight (Mn) of 22,000 or higher, preferably 23,500 or higher, and a ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) of 2.54 or less, preferably 2.50 or less. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an aromatic polysulfone resin suitable as a membrane material and a membrane using the same.

  Aromatic polysulfone resins are used in various applications because of their excellent heat resistance and chemical resistance. One of the applications is a porous membrane material used for filtration such as ultrafiltration and microfiltration. For example, JP 2006-230459 A (Patent Document 1) discloses a porous hollow fiber membrane. As the material, it is described that an aromatic polysulfone resin is used, and specifically, an example using an aromatic polysulfone resin having a reduced viscosity of 0.36, 0.48, or 0.52 is shown. Yes.

JP 2006-230459 A

  Porous membranes that have been clogged by prolonged use for filtration and have reduced filtration efficiency are usually washed by backflowing air or water to eliminate the clogging. A porous membrane made of a polysulfone resin does not necessarily have sufficient toughness of an aromatic polysulfone resin. Therefore, if excessive pressure is applied during cleaning, breakage such as cutting or tearing may occur. Accordingly, an object of the present invention is to provide an aromatic polysulfone resin having high toughness and suitable as a material for a membrane including a porous membrane.

  In order to achieve the above object, the present invention has a reduced viscosity of 0.55 to 0.65 dL / g, a number average molecular weight (Mn) of 22,000 or more, and a weight average molecular weight (Mw) relative to the number average molecular weight (Mn). ) Ratio value is 2.54 or less, an aromatic polysulfone resin is provided. Moreover, according to this invention, the film | membrane containing the said aromatic polysulfone resin is also provided.

  Since the aromatic polysulfone resin of the present invention has high toughness, it is suitably used as a material for membranes including porous membranes.

The aromatic polysulfone resin has a repeating unit containing a divalent aromatic group (residue obtained by removing two hydrogen atoms bonded to the aromatic ring from an aromatic compound) and a sulfonyl group (—SO ₂ —). Resin. In the aromatic polysulfone resin of the present invention, from the viewpoint of heat resistance and chemical resistance, the repeating unit is a repeating unit represented by the following formula (1) (hereinafter sometimes referred to as “repeating unit (1)”). The repeating unit represented by the following formula (2) (hereinafter sometimes referred to as “repeating unit (2)”) or the repeating unit represented by the following formula (3) (hereinafter referred to as “ Other repeating units such as “repeating unit (3)” may be included. The aromatic polysulfone resin of the present invention preferably has 50 to 100 mol%, more preferably 80 to 100 mol% of the repeating unit (1) with respect to the total of all repeating units.

_{^{-Ph 1 -SO 2 -Ph 2 -O- (}} 1)

(Ph ¹ and Ph ² each independently represent a phenylene group. The hydrogen atoms in the phenylene group may each independently be substituted with an alkyl group, an aryl group, or a halogen atom.)

-Ph ³ -R-Ph ⁴ -O- (2)

(Ph ³ and Ph ⁴ each independently represent a phenylene group. The hydrogen atoms in the phenylene group may each independently be substituted with an alkyl group, an aryl group or a halogen atom. R represents an alkylidene. Represents a group, oxygen atom or sulfur atom.)

-(Ph ⁵ ) _n -O- (3)

(Ph ⁵ represents a phenylene group. Each hydrogen atom in the phenylene group may be independently substituted with an alkyl group, an aryl group or a halogen atom. N represents an integer of 1 to 3. When n is 2 or more, a plurality of Ph ⁵ may be the same or different from each other.)

The phenylene group represented by any of Ph ^{1 to} Ph ⁵ may be a p-phenylene group, an m-phenylene group, or an o-phenylene group. -A phenylene group is preferred. Examples of the alkyl group which may substitute a hydrogen atom in the phenylene group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, and a t-butyl group. A butyl group is mentioned, The carbon number is 1-5 normally. Examples of the aryl group that may substitute a hydrogen atom in the phenylene group include a phenyl group, a 1-naphthyl group, a 2-naphthyl group, and a p-toluyl group, and the number of carbon atoms is usually 6-15. It is. Examples of the alkylidene group represented by R include a methylene group, an ethylidene group, an isopropylidene group, and a 1-butylidene group, and the number of carbon atoms is usually 1-5.

  The aromatic polysulfone resin of the present invention has a reduced viscosity of 0.55 to 0.65 dL / g, preferably 0.58 to 0.62 dL / g. When the reduced viscosity is outside the above range, the toughness of the aromatic polysulfone resin becomes insufficient. On the other hand, when the reduced viscosity exceeds the upper limit, the processability of the aromatic polysulfone resin becomes insufficient.

  The aromatic polysulfone resin of the present invention has a number average molecular weight (Mn) of 22000 or more, preferably 23500 or more. If Mn is less than the lower limit, the toughness of the aromatic polysulfone resin becomes insufficient. In addition, although the upper limit of Mn is adjusted suitably, from the point of the workability of aromatic polysulfone resin, it is 30000 normally, Preferably it is 27000.

  Furthermore, the value (Mw / Mn) of the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the aromatic polysulfone resin of the present invention is 2.54 or less, preferably 2.50 or less. When Mw / Mn exceeds the upper limit, the toughness of the aromatic polysulfone resin becomes insufficient. In addition, the minimum of Mw / Mn is 1 theoretically, and it is so preferable that it is close to 1.

  The aromatic polysulfone resin can be suitably produced by polycondensing a corresponding aromatic dihalogenosulfone compound and an aromatic dihydroxy compound in an organic polar solvent using an alkali metal carbonate as a base. it can. For example, a resin having a repeating unit (1) uses a compound represented by the following formula (4) as an aromatic dihalogenosulfone compound (hereinafter sometimes referred to as “compound (4)”), and an aromatic dihydroxy compound. Can be preferably produced by using a compound represented by the following formula (5) (hereinafter sometimes referred to as “compound (5)”). The resin having the repeating unit (1) and the repeating unit (2) uses the compound (4) as the aromatic dihalogenosulfone compound, and the compound represented by the following formula (6) as the aromatic dihydroxy compound (hereinafter referred to as the aromatic dihydroxy compound). , Sometimes referred to as “compound (6)”. In addition, the resin having the repeating unit (1) and the repeating unit (3) uses the compound (4) as the aromatic dihalogenosulfone compound and the compound represented by the following formula (7) as the aromatic dihydroxy compound (hereinafter referred to as the aromatic dihydroxy compound). , Sometimes referred to as “compound (7)”).

_{^{X 1 -Ph 1 -SO 2 -Ph 2}} -X 2 (4)

(X ¹ and X ² each independently represent a halogen atom. Ph ¹ and Ph ² are as defined above.)

HO—Ph ¹ —SO ₂ —Ph ² —OH (5)

(Ph ¹ and Ph ² are as defined above.)

^{HO-Ph 3 -R-Ph 4} -OH (6)

(Ph ³ , Ph ⁴ and R are as defined above.)

HO— (Ph ⁵ ) _n —OH (7)

(Ph ⁵ and n are as defined above.)

  Examples of compound (4) include bis (4-chlorophenyl) sulfone and 4-chlorophenyl-3 ', 4'-dichlorophenylsulfone. Examples of the compound (5) include bis (4-hydroxyphenyl) sulfone, bis (4-hydroxy-3,5-dimethylphenyl) sulfone, and bis (4-hydroxy-3-phenylphenyl) sulfone. Examples of the compound (6) include 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxyphenyl) hexafluoropropane, bis (4-hydroxyphenyl) sulfide, bis (4- Hydroxy-3-methylphenyl) sulfide and bis (4-hydroxyphenyl) ether. Examples of the compound (7) include hydroquinone, resorcin, catechol, phenylhydroquinone, 4,4′-dihydroxybiphenyl, 2,2′-dihydroxybiphenyl, 3,5,3 ′, 5′-tetramethyl-4,4. Examples include '-dihydroxybiphenyl, 2,2'-diphenyl-4,4'-dihydroxybiphenyl, and 4,4' ''-dihydroxy-p-quarterphenyl.

  Examples of aromatic dihalogenosulfone compounds other than compound (4) include 4,4'-bis (4-chlorophenylsulfonyl) biphenyl. Moreover, it replaces with all or one part of an aromatic dihalogeno sulfone compound and / or an aromatic dihydroxy compound, and has halogeno groups and hydroxyl groups in molecules, such as 4-hydroxy-4 '-(4-chlorophenylsulfonyl) biphenyl. Compounds can also be used.

  The alkali metal carbonate may be an alkali carbonate that is a normal salt, an alkali bicarbonate (an alkali hydrogen carbonate) that is an acidic salt, or a mixture of both. As the alkali carbonate, sodium carbonate or potassium carbonate is preferably used, and as the alkali bicarbonate, sodium bicarbonate or potassium bicarbonate is preferably used.

  Examples of the organic polar solvent include dimethyl sulfoxide, 1-methyl-2-pyrrolidone, sulfolane (1,1-dioxothyrane), 1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidi. Non, dimethyl sulfone, diethyl sulfone, diisopropyl sulfone and diphenyl sulfone can be mentioned.

  The usage-amount of an aromatic dihalogeno sulfone compound is 95-110 mol% normally with respect to an aromatic dihydroxy compound, Preferably it is 100-105 mol%. The target reaction is dehydrohalogenated polycondensation of an aromatic dihalogenosulfone compound and an aromatic dihydroxy compound. If no side reaction occurs, the closer the molar ratio of the two is to 1: 1, that is, the aromatic As the amount of the aromatic dihalogenosulfone compound used is closer to 100 mol% with respect to the aromatic dihydroxy compound, the resulting aromatic polysulfone resin has a higher degree of polymerization, resulting in higher reduced viscosity and higher Mn. Mw / Mn tends to be small, but in fact, side reaction such as substitution reaction of halogeno group to hydroxyl group or depolymerization occurs due to by-produced alkali hydroxide or the like. Since the degree of polymerization of the aromatic polysulfone resin is reduced, the degree of this side reaction is also taken into consideration and the aromatic polymer having the predetermined reduced viscosity, Mn, and Mw / Mn. As sulfone resin can be obtained, it is necessary to adjust the amount of the aromatic dihalogenosulfone compound.

  The usage-amount of the alkali metal salt of carbonic acid is 95-115 mol% normally as an alkali metal with respect to the hydroxyl group of an aromatic dihydroxy compound, Preferably it is 100-110 mol%. If no side reaction occurs, the greater the amount of alkali metal carbonate used, the faster the desired polycondensation will proceed, and the resulting aromatic polysulfone resin will have a higher degree of polymerization, resulting in reduction. Viscosity increases, Mn increases, and Mw / Mn tends to decrease, but in fact, the larger the amount of alkali metal salt of carbonic acid used, the easier the side reaction similar to the above occurs. Since the degree of polymerization of the resulting aromatic polysulfone resin is reduced, the degree of this side reaction is also taken into consideration so that the aromatic polysulfone resin having the predetermined reduced viscosity, Mn and Mw / Mn can be obtained. It is necessary to adjust the amount of metal salt used.

  In a typical process for producing an aromatic polysulfone resin, as a first step, an aromatic dihalogenosulfone compound and an aromatic dihydroxy compound are dissolved in an organic polar solvent, and as a second step, a solution obtained in the first step An alkali metal salt of carbonic acid is added to polycondensate the aromatic dihalogenosulfone compound and the aromatic dihydroxy compound. As a third step, an unreacted carbonic acid alkali is obtained from the reaction mixture obtained in the second step. An aromatic polysulfone resin is obtained by removing the metal salt, the by-produced alkali halide, and the organic polar solvent.

  The melting temperature in the first stage is usually 40 to 180 ° C. The polycondensation temperature in the second stage is usually 180 to 400 ° C. If no side reaction occurs, the higher the polycondensation temperature, the faster the target polycondensation proceeds, so the resulting aromatic polysulfone resin has a higher degree of polymerization, resulting in a higher reduced viscosity, Although Mn tends to increase and Mw / Mn tends to decrease, in fact, the higher the polycondensation temperature, the more likely the side reaction similar to the above occurs, and this side reaction causes the degree of polymerization of the aromatic polysulfone resin to be obtained. Therefore, it is necessary to adjust the polycondensation temperature so that the aromatic polysulfone resin having the predetermined reduced viscosity, Mn and Mw / Mn can be obtained in consideration of the degree of this side reaction.

  In the second stage polycondensation, usually, the temperature is gradually raised while removing by-product water, and after reaching the reflux temperature of the organic polar solvent, it is usually 1 to 50 hours, preferably 10 to 30 hours. It is better to keep it warm. If no side reaction occurs, the longer the polycondensation time, the more the target polycondensation proceeds. Therefore, the resulting aromatic polysulfone resin has a higher degree of polymerization, resulting in a higher reduced viscosity and a higher Mn. Mw / Mn tends to decrease, but in fact, the longer the polycondensation time, the more the same side reaction proceeds, and this side reaction reduces the degree of polymerization of the resulting aromatic polysulfone resin. In consideration of the degree of side reaction, it is necessary to adjust the polycondensation time so that the aromatic polysulfone resin having the predetermined reduced viscosity, Mn and Mw / Mn can be obtained.

  In the third stage, the aromatic polysulfone is first removed from the reaction mixture obtained in the second stage by removing unreacted alkali metal salt of carbonic acid and by-produced alkali halide by filtration or centrifugation. A solution in which the resin is dissolved in an organic polar solvent can be obtained. Subsequently, an aromatic polysulfone resin can be obtained by removing the organic polar solvent from this solution. The removal of the organic polar solvent may be carried out by directly distilling off the organic polar solvent from the solution, or the solution is mixed with a poor solvent for the aromatic polysulfone resin to precipitate the aromatic polysulfone resin. You may carry out by isolate | separating by filtration, centrifugation, etc.

  Examples of the poor solvent for the aromatic polysulfone resin include methanol, ethanol, isopropyl alcohol, hexane, heptane, and water, and methanol is preferable because it can be easily removed.

  When a relatively high melting point organic polar solvent is used as a polymerization solvent, the reaction mixture obtained in the second stage is cooled and solidified, and then pulverized. From the obtained powder, water is used. In addition, an alkali metal salt of unreacted carbonic acid and a by-produced alkali halide are extracted and removed, and a solvent that does not have solubility in aromatic polysulfone resin and has solubility in organic polar solvent. It is also possible to extract and remove the organic polar solvent.

  The volume average particle diameter of the powder is preferably 200 to 2000 μm, more preferably 250 to 1500 μm, and further preferably 300 to 1000 μm from the viewpoint of extraction efficiency and workability during extraction. If it is too large, the extraction efficiency is poor, and if it is too small, it is not preferred because it solidifies during extraction or clogs when filtering or drying after extraction.

  As the extraction solvent, for example, when diphenyl sulfone is used as the polymerization solvent, a mixed solvent of acetone and methanol can be used. Here, the mixing ratio of acetone and methanol is usually determined from the extraction efficiency and the sticking property of the aromatic polysulfone resin powder.

  In another typical method for producing an aromatic polysulfone resin, as a first step, an aromatic dihydroxy compound and an alkali metal carbonate are reacted in an organic polar solvent to remove by-product water, As the second stage, an aromatic dihalogenosulfone compound is added to the reaction mixture obtained in the first stage to perform polycondensation, and as the third stage, from the reaction mixture obtained in the second stage as described above, Unreacted alkali metal salt of carbonic acid, by-produced alkali halide and organic polar solvent are removed to obtain an aromatic polysulfone resin.

  In this alternative method, in the first stage, an azeotropic dehydration may be performed by adding an organic solvent azeotropic with water in order to remove by-product water. Examples of the organic solvent azeotropic with water include benzene, chlorobenzene, toluene, methyl isobutyl ketone, hexane and cyclohexane. The temperature of azeotropic dehydration is usually 70 to 200 ° C.

  In this alternative method, the polycondensation temperature in the second stage is usually 40 to 180 ° C., and the fragrance having the predetermined reduced viscosity, Mn, and Mw / Mn is taken into consideration in the same manner as described above in consideration of the degree of side reaction. It is necessary to adjust the polycondensation temperature and the polycondensation time so that the group polysulfone resin can be obtained.

  The aromatic polysulfone resin of the present invention thus obtained has high toughness, and therefore can be used for various applications, and can be particularly suitably used as a material for membranes including porous membranes.

  The membrane containing the aromatic polysulfone resin of the present invention may be, for example, a flat membrane, a tubular membrane, a hollow fiber membrane, or a single layer membrane. It may be a multilayer film. In addition, when it is a multilayer film, it may be a multilayer film having only two or more layers containing the aromatic polysulfone resin of the present invention, or may have one or more layers containing the aromatic polysulfone resin of the present invention, Further, it may be a multilayer film having one or more other layers.

  For the production of the membrane, known methods can be appropriately employed. For the production of the porous membrane, for example, an aromatic polysulfone resin is dissolved in a solvent, this solution is extruded into a predetermined shape, and dried and wetted through an air gap. It may be carried out by introducing into a coagulating liquid by a formula or wet without passing through an air gap, and by performing phase separation and desolvation, or by dissolving an aromatic polysulfone resin in a solvent, It may be carried out by casting it on a base material, immersing it in a coagulation liquid, phase separation and desolvation. The non-porous membrane may be produced, for example, by melting an aromatic polysulfone resin and extruding it into a predetermined shape, or by melting the aromatic polysulfone resin and casting it onto a substrate having a predetermined shape. Alternatively, it may be performed by dissolving the aromatic polysulfone resin in a solvent, casting the solution on a substrate having a predetermined shape, and removing the solvent.

  Further, when producing a hollow fiber membrane as a porous membrane, the solution is used as a spinning stock solution, and a core-sheath type double annular nozzle is used to discharge the solution from the sheath side, and a coagulating liquid (hereinafter referred to as the core side). , Sometimes referred to as “internal coagulating liquid”) or by discharging gas and introducing them into the coagulating liquid (hereinafter also referred to as “external coagulating liquid”) with or without an air gap. preferable.

  Examples of the good solvent for the aromatic polysulfone resin used in the preparation of the solution (hereinafter sometimes simply referred to as “good solvent”) include N-methylpyrrolidone, N, N-dimethylformamide, and N, N-dimethylacetamide. Is mentioned. In particular, when producing a porous membrane, the solution contains components other than the aromatic polyester resin and the good solvent, such as a poor solvent for the hydrophilic polymer and the aromatic polysulfone resin (hereinafter simply referred to as “poor solvent”). In some cases, a swelling agent may be contained. By containing a hydrophilic polymer in the solution, a porous membrane that is excellent in water permeability and can be suitably used for filtration such as ultrafiltration or microfiltration of an aqueous fluid can be obtained. In addition, when a poor solvent or a swelling agent is not contained in the solution, it is preferable to use N, N-dimethylacetamide as a good solvent.

  Examples of hydrophilic polymers include polyvinyl pyrrolidone, polyalkylene glycols such as polyethylene glycol and polypropylene glycol, polyvinyl alcohol, polyhydroxyalkyl (meth) acrylates such as polyhydroxyethyl acrylate and polyhydroxyethyl methacrylate, polyacrylamide and polyethyleneimine. And two or more of them may be used as necessary. Among them, it is preferable to use polyvinyl pyrrolidone, particularly high molecular weight polyvinyl pyrrolidone having a molecular weight of 1,000,000 to 3,000,000 because the thickening effect of the solution can be enhanced even if its content is small.

  The usage-amount of a hydrophilic polymer is 5-40 weight part normally with respect to 100 weight part of aromatic polysulfone resin, Preferably it is 15-30 weight part. If the amount of the hydrophilic polymer used is too small, the water permeability of the resulting porous membrane will be insufficient, and if it is too large, the heat resistance, chemical resistance, and toughness of the resulting porous membrane will be insufficient. Become.

  Examples of the swelling agent include ethylene glycols such as ethylene glycol, diethylene glycol, and triethylene glycol, and ethylene glycol is preferable because it can be easily removed.

  As the coagulation liquid, a poor solvent or a mixed solvent of a poor solvent and a good solvent can be used, but when a mixed solvent of a poor solvent and a good solvent is used as the coagulation liquid, the mixing ratio thereof can be adjusted. The pore size and pore size distribution of the resulting porous membrane can be adjusted, and in particular, both the internal coagulating liquid and the external coagulating liquid are composed of water as a poor solvent and N, N-dimethylacetamide as a good solvent. When a mixed solvent is used, these effects can be efficiently extracted. Further, by using this mixed solvent, subsequent solvent recovery can be easily performed.

  When a porous membrane is produced by adding a hydrophilic polymer to the solution, the obtained porous membrane may be subjected to heat treatment or insolubility treatment to insolubilize the hydrophilic polymer in the porous membrane, if necessary. Radiation treatment may be performed. By performing heat treatment or radiation treatment, the hydrophilic polymer is cross-linked and fixed in the porous membrane, so when using the porous membrane as a filtration membrane, the hydrophilic polymer is eluted in the filtrate. Can be prevented.

  The heat treatment or radiation treatment is preferably performed under conditions in which the porous film is not significantly changed in shape, structure, mechanical properties, etc., and is sufficient for the hydrophilic polymer to be crosslinked. Only one process may be performed, or both processes may be performed.

  For example, the heat treatment of the porous membrane produced using polyvinylpyrrolidone as the hydrophilic polymer is preferably performed at a treatment temperature of 150 to 190 ° C., and the treatment time is appropriately set depending on the amount of polyvinylpyrrolidone in the porous membrane. The

  In addition, the radiation treatment of the porous film can be performed using α rays, β rays, γ rays, X rays, or electron rays as the radiation. In this case, damage to the porous membrane can be effectively prevented by carrying out the treatment in a state where the porous membrane is impregnated with the antioxidant-containing water.

  Examples of the present invention will be described below, but the present invention is not limited thereto.

(Measurement of reduced viscosity of aromatic polysulfone resin)
About 1 g of the aromatic polysulfone resin was dissolved in N, N-dimethylformamide to make the volume 1 dL, and the viscosity (η) of this solution was measured at 25 ° C. using an Ostwald type viscosity tube. Further, the viscosity (η ₀ ) of N, N-dimethylformamide as a solvent was measured at 25 ° C. using an Ostwald type viscosity tube. From the viscosity (η) of the solution and the viscosity (η ₀ ) of the solvent, the specific viscosity ((η−η ₀ ) / η ₀ ) is obtained, and this specific viscosity is calculated as the concentration of the solution (about 1 g / dL). ) To determine the reduced viscosity (dL / g) of the aromatic polysulfone resin.

[Measurement of Mn and Mw / Mn of aromatic polysulfone resin]
Gel permeation chromatography (GPC) analysis was performed under the following conditions, Mn and Mw were determined, and Mw / Mn was calculated (average value of the number of analyzes twice).
Sample: 50 μL of N, N-dimethylformamide solution of aromatic polysulfone resin having a concentration of 0.002 g / mL Column: Two “TSKgel GMH _HR- H” (7.8 mmφ × 300 mm) manufactured by Tosoh Corporation Connecting column temperature: 40 ° C
Eluent: N, N-dimethylformamide Eluent flow rate: 0.8 mL / min Detector: differential refractometer (RI) + light scattering photometer (LS)
Standard reagent: Polystyrene

[Evaluation of toughness of aromatic polysulfone resin]
A 13 cm x 1 cm test piece was cut out from the aromatic polysulfone resin membrane and subjected to a bending test using a MIT fatigue resistance tester (manufactured by Toyo Seiki Co., Ltd.) under a bending radius of 0.38 mm and a load of 4.9 N. Then, the number of bending until the test piece broke was obtained (average value of 8 tests).

Example 1
In a polymerization tank equipped with a stirrer, a nitrogen introduction tube, a thermometer, and a condenser with a receiver at the tip, 500 g of bis (4-hydroxyphenyl) sulfone, 589 g of bis (4-chlorophenyl) sulfone, and diphenyl as a polymerization solvent 942 g of sulfone was charged, and the temperature was raised to 180 ° C. while flowing nitrogen gas through the system. After adding 287 g of potassium carbonate to the obtained solution, the temperature was gradually raised to 290 ° C., and the mixture was further reacted at 290 ° C. for 2 hours. The obtained reaction solution was cooled to room temperature, solidified, finely pulverized, washed with warm water and washed with a mixed solvent of acetone and methanol several times, then heated and dried at 150 ° C., and the terminal was a chloro group. An aromatic polysulfone resin was obtained as a powder. The reduced viscosity, Mn, and Mw / Mn of this aromatic polysulfone resin were measured, and the results are shown in Table 1.

  In a 500 mL separable flask, 75 g of the aromatic polysulfone resin and 225 g of N-methyl-2-pyrrolidone were added and stirred at 60 ° C. for 2 hours to obtain a pale yellow aromatic polysulfone solution. This solution was cast on a glass plate (thickness 3 mm) using a film applicator, heated at 60 ° C. using a high-temperature hot air dryer until the surface was dried, and then heat-treated at 250 ° C. in a nitrogen atmosphere. An aromatic polysulfone resin film having a thickness of 46 μm was formed on a glass plate. Subsequently, the aromatic polysulfone resin film was peeled off from the glass plate, the toughness was evaluated, and the results are shown in Table 1.

Comparative Example 1
In a polymerization tank equipped with a stirrer, a nitrogen introduction tube, a thermometer, and a condenser with a receiver at the tip, 500 g of bis (4-hydroxyphenyl) sulfone, 593 g of bis (4-chlorophenyl) sulfone, and diphenyl as a polymerization solvent 949 g of sulfone was charged, and the temperature was raised to 180 ° C. while flowing nitrogen gas through the system. After adding 287 g of anhydrous potassium carbonate to the obtained solution, the temperature was gradually raised to 290 ° C., and the mixture was further reacted at 290 ° C. for 2 hours. The obtained reaction solution was cooled to room temperature, solidified, finely pulverized, washed with warm water and washed with a mixed solvent of acetone and methanol several times, then heated and dried at 150 ° C., and the terminal was a chloro group. An aromatic polysulfone resin was obtained as a powder. The reduced viscosity, Mn, and Mw / Mn of this aromatic polysulfone resin were measured, and the results are shown in Table 1.

  Using the aromatic polysulfone resin, an aromatic polysulfone resin film was obtained in the same manner as in Example 1, the toughness was evaluated, and the results are shown in Table 1.

Comparative Example 2
A commercially available aromatic polysulfone resin (“Ultrason E6020P” manufactured by BASF) was used. The reduced viscosity, Mn, and Mw / Mn of this aromatic polysulfone resin were measured, and the results are shown in Table 1.

  Using the aromatic polysulfone resin, an aromatic polysulfone resin film was obtained in the same manner as in Example 1, the toughness was evaluated, and the results are shown in Table 1.

Claims (4)

  The reduced viscosity is 0.55 to 0.65 dL / g, the number average molecular weight (Mn) is 22,000 or more, and the value (Mw / Mn) of the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is An aromatic polysulfone resin having a viscosity of 2.54 or less. The aromatic polysulfone resin of Claim 1 which has a repeating unit represented by following formula (1).
_{^{-Ph 1 -SO 2 -Ph 2 -O- (}} 1)
(Ph ¹ and Ph ² each independently represent a phenylene group. The hydrogen atoms in the phenylene group may each independently be substituted with an alkyl group, an aryl group, or a halogen atom.)   A membrane comprising the aromatic polysulfone resin according to claim 1 or 2.   The membrane according to claim 3, which is a porous membrane.